In this study, we characterized ammonia and ammonium (NH₃/NH₄⁺) transport by the Rhesus Associated Glycoproteins RhAG, Rhbg and Rhcg expressed in Xenopus oocytes. To do so we used ion-selective microelectrodes & two-electrode voltage clamp to measure changes in intracellular pH (pH_i), surface pH (pHs) and whole cell currents (I) induced by NH3/NH₄⁺ and methyl amine/ammonium (MA/MA⁺). These measurements allowed us to define signal-specific signatures to distinguish NH₃ from NH₄⁺ transport and to determine how transport of NH₃ and NH₄⁺ differ among RhAG, Rhbg and Rhcg. Our data indicated that expressing Rh glycoproteins in oocytes generally enhanced NH3/NH₄⁺ transport and that transport of MA/MA+ by Rh proteins induced different cellular changes than transport of NH3/NH₄⁺. Our results support the following conclusions: 1) RhAG and Rhbg transport both the ionic NH₄⁺ and neutral NH3 species. 2) Transport of NH₄⁺ is electrogenic. 3) Like Rhbg, RhAG transport of NH₄⁺ masks NH3 transport. 4) Rhcg is likely to be a predominantly NH₃ transporter with no evidence of enhanced NH₄⁺ transport by this transporter. The dual role of Rh proteins as NH₃ and NH₄⁺ transporters is a unique property and may be critical in understanding how transepithelial secretion of NH₃/NH₄⁺ occurs in the renal collecting duct.